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MT Generate Symbol Map (Circular) (G Dataflow)

Last Modified: January 9, 2017

Generates a symbol map, using the matrix of symbol values that you specify, a matrix representing the symbol phases in degrees, and an array representing the radii of each discrete circle. Use the symbol map parameter of the system parameters cluster to configure the operation of the demodulation and modulation nodes.

The symbol values matrix defines how the M-ary binary data are mapped to the discrete I/Q symbols on the constellation diagram. The node maps the specified symbol values to I/Q constellation points using the polar representation j π θ i 180 . The node reads the symbol values/symbol phases matrices row-wise. Each row of symbol values/symbol phases is then mapped onto I/Q symbol points, which are located on a circle with a radius that is specified in the symbol radii array.

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The dimensions of the symbol amplitudes matrix must exactly match the dimensions of the symbol phases matrix. Additionally, the number of rows of each matrix must be equal the length of the symbol radii array. If these conditions are violated, the node returns an error.

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symbol values

A matrix of integers that define how the M-ary (bits per symbol) binary data are mapped to discrete I/Q symbols on the constellation diagram. Use negative values to specify holes (missing points) in the constellation diagram.

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The binary representation of the symbol values is performed using the LSB first convention. For example, in 8-QAM, the symbol values matrix can be specified as

[ 0 1 2 3 1 4 5 6 7 ]

This matrix corresponds to the following bit values:

[ 000 100 010 110 X X X 001 101 011 111 ]

The term XXX here refers to a hole (missing point) on the constellation plot.

Default: empty

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symbol phases

Phases, in degrees, corresponding to the location of the elements of the symbol values matrix on the I/Q constellation diagram.

Default: empty

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symbol radii

Radii of discrete concentric circles that contain the I/Q constellation points. There is a one-to-one mapping between every entry on the symbol radii array and every row in the symbol values/symbol phases matrix.

Default: empty

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error in

Error conditions that occur before this node runs. The node responds to this input according to standard error behavior.

Default: no error

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symbol map

An ordered array to be bundled with the system parameters cluster that is passed to the digital demodulation and modulation nodes.

The generated symbol maps must be bundled onto the system parameters cluster prior to being passed to the corresponding modulation node.

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error out

Error information. The node produces this output according to standard error behavior.

Generic or Combined Amplitude Modulation Scheme

Use MT Generate Symbol Map (Rectangular) to create a custom symbol map for a generic amplitude modulation scheme such as quadrature amplitude modulation (QAM). Use MT Generate Symbol Map (Circular) to create a custom symbol map for a combined amplitude-phase modulation scheme.

Example: 8-QAM Symbol Map Creation

The following example demonstrates 8-QAM symbol map creation. Define the symbol values as [ 0 1 2 3 1 4 5 6 7 ] .

Define the I symbol amplitude array as [ 1 0 1 ] .

Define the Q symbol amplitude array as [ 1 0 1 ] .

Define gain as 1.0.

These settings result in the following symbol map.

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported


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